Separate authors have reported that knee extension dominates power production during submaximal cycling (SUBcyc) and hip extension is the dominant action during maximal cycling (MAXcyc). Changes in joint-specific powers across broad ranges of net cycling powers (Pnet) within one group of cyclists have not been reported.
Purpose: Our purpose was to determine the extent to which ankle, knee, and hip joint actions produced power across a range of Pnet. We hypothesized that relative knee extension power would decrease and relative knee flexion and hip extension powers would increase as Pnet increased.
Methods: Eleven cyclists performed SUBcyc (250, 400, 550, 700, and 850 W) and MAXcyc trials at 90 rpm. Joint-specific powers were calculated and averaged over complete pedal revolutions and over extension and flexion phases. Portions of the cycle spent in extension (duty cycle) were determined for the whole leg and ankle, knee, and hip joints. Relationships of relative joint-specific powers with Pnet were assessed with linear regression analyses.
Results: Absolute ankle, knee, and hip joint-specific powers increased as Pnet increased. Relative knee extension power decreased (r2 = 0.88, P = 0.01) and knee flexion power increased (r2 = 0.98, P < 0.001) as Pnet increased. Relative hip extension power was constant across all Pnet. Whole-leg and ankle, knee, and hip joint duty cycle values were greater for MAXcyc than for SUBcyc.
Conclusions: Our data demonstrate that 1) absolute ankle, knee, and hip joint-specific powers substantially increase as a function of increased Pnet, 2) hip extension was the dominant power-producing action during SUBcyc and MAXcyc, 3) knee flexion power becomes relatively more important during high-intensity cycling, and 4) increased duty cycle values represent an important strategy to increase maximum power.